Artificial Limbs: When his hand is chopped off, Ash replaces it with a chainsaw. Later, he replaces that with a clockwork gauntlet.

And in the extended media beyond the films, he'll frequently swap out his gauntlet with the saw.

Ax Crazy: How Ash copes with the events of the first two movies. By the third, he's turned it into Crazy Awesome.

A further explanation, using the last entry, the difference between Ax Crazy and Crazy Awesome:

[Pic of Jack Nicholson's character in the Shining] An "ax crazy" character is someone who is psychologically unstable and presents a clear danger to others. Ax crazies are capable of extreme violence, whether carried out with a Slasher Smile, a Creepy Monotone, or out and out murderous rage, and they're not too picky about their victims, which makes them extremely frightening to deal with. This mainly differentiates them from other eccentric characters who may themselves be obsessive, weird or seemingly crazy, but use this condition hand in hand with doing good, or at least not being in the way. However, some formerly established heroes can go through an episode of ax-craziness and still retain their heroic mantle.

vs.

Someone who is Crazy Awesome is someone who's nucking futs, in an amusing way, and is effective at what he does because of that craziness. In real life he'd get fired from whatever job he has/would have, or even arrested — at the very least, the things he does just plain wouldn't work. But somehow, he manages to be both effective and a character that the audience likes or even loves.

Like any good internet resource (especially those made by My GenX Brethren), each entry is hyperlinked to a bunch of other concepts. I declare this website, fun.